Fix all Doxygen errors and make any future errors fatal (#118) ...

* Start working on fixing doxygen warnings

* Upgrade doxyfile to Doxygen 1.9.1

* Clean up some unmatched groups and add some exclusions

* Fix docs for rtos::ThisThread not showing up

* Fix up KV store docs

* Fix incorrect @files, some more incorrect groups

* Fix lots of broken links

* Start fixing mbedtls groups

* Fix more mbedtls docs

* Fix remaining mbedtls files with missing or incorrect grouping

* Fix a huge amount of PSA docs errors

* Fix a few more mbedtls docs errors

* Fix __cplusplus not defined for docs, clean up call in callback typedef, fix some docs errors

* Fix some broken doc links in HAL headers

* Fix more PSA doc errors

* Fix some doxygen errors in networking code

* Fix lots of network related doc errors

* Try and fix some CI failures

* Use Doxygen Action instead of doxygen in Mbed container to get the right version

* Try removing docs check

* Add first part of doxygen action

* Add next part of doxygen action

* Fix yaml syntax error

* Add in license check fix

* Try using verbose scancode

* Fix some more docs issues, workaround scancode-toolkit#3179

* Clean up the LoRaRadio get_state() function on each implementation.  Also fix some other compile and doc errors.

* Fix all remaining doxygen errors

* Fix escaping, for realsies this time

* Remove Doxygen unsupported config options, fix some more get_status() declarations

* Fix some UNITTESTS build errors

* Fix one more compile error

* Another unittest error

Fix a few mistakes in the I2C docs. (#66)

Lots of usability improvements for the I2C API. Better docs and new top-level functions. (#64) ...

* Lots of usability improvements for the I2C API.  Better docs and new top-level functions.

* Document frequencies

* Tabs to spaces

* More style fixes

* Run astyle

* Clean up docs

* Add note about addressing, change 10 bit to 11 bit

* Fix spellcheck

* Fix paste error

* Oops, fix accidental change

Fix ABI differences between mbed-baremetal and mbed-os, remove PlatformMutex

Fix hanging with multiple I2C buses ...

Make the _mutex non-static and remove _owner and acquire()

When two or more I2C buses are used then static__mutex and _owner are
shared between all I2C class instances in the program. That
wastes time to reconfigure periphery on every transfer.

Make _mutex non-static. Remove _owner and acquire() method
because in non-static case they have no practical meaning.

Move drivers headers